The practice of treating seeds or other plant propagation material with pesticide formulations is well known. Insecticides and fungicides are applied to seeds to protect them from pests through the early stages of plant development in the soil. Two types of pesticide formulations are typically used: wettable powders and aqueous flowables.
Commercial seed treatment formulations require specialized equipment to properly apply them or to treat large volumes of seed. The seed treatment equipment (a seed treater) combines commercially available formulations to make slurries of pesticides. Examples of seed treaters include Gustafson Accu-Treat® RH-24 seed treater (Accu Treat is a registered trademark of Bayer CropScience), Accu-Coat HC 3000 seed treater and the like. A commercial pesticide formulation is usually formulated as a suspension concentrate. A seed treater is also used to add stickers, binders, polymers, and/or colorants to the pesticide slurry to improve handling and safety. The additives reduce dusting, and the colorants alert agricultural workers to the chemical treatment.
The number of additives and the amount of pesticide per seed that can be used in seed applications is limited by the coating and drying techniques available for use with commercial seed treating equipment. Each crop can adsorb just a limited amount of fluid, beyond which the seeds cannot be properly dried and/or handled in the seed processing equipment or planting equipment.
Furthermore, many existing formulations contain high concentrations of low molecular weight (LMW) surfactants. These LMW surfactants are typically added to stabilize the dispersion of the pesticide and to provide a stable pumpable suspension for ease of use by the treater. One of the problems associated with LMW surfactants is that they are known to increase the stress on seeds and can reduce germination.
In addition, it is known that a stable aqueous formulation is not easily obtained for certain pesticidal agents that have relatively higher water solubility and/or lower melting point. Metalaxyl (mp 63-72° C. for the technical grade, water solubility 8400 ppm) is one of such chemicals. Obtaining stable aqueous suspension formulations of metalaxyl is very challenging because there is no good way to prevent the chemical from re-crystallizing out, causing physical instability during storage.
Another problem with using ad hoc mixtures of pesticides, polymers, colorants, and other additives is the need for multiple applications to deposit and dry the desired amounts of pesticides and additives on the seeds. Multiple applications are necessary for proper adhesion.
In addition to being time consuming, the safety of these application mixtures is often unknown and problematic. Often, fillers, such as talc, are needed to reduce phytotoxicity or to improve seed drying and handling properties. As a result, handling is rendered difficult and the biological efficacy of the seed treatment is reduced.
There is still a need in the art for ready-to-use and effective non-phytotoxic all-inclusive formulations that adhere pesticides to seeds and eliminate the need to add further binders or polymers to the application mixture by a seed treater. Ideally, such a formulation can be processed in continuous flow in a single-pass application without fillers or anti-blocking powders.